Solvent can be removed from a polymer solution (or, in other words, polymer can be recovered from a solution) by employing a particle form evaporation process. Particle form evaporation is described, for example, in U.S. Pat. Nos. 4,310,973 and 4,263,091, incorporated by reference herein. Broadly, particle form evaporation involves introducing a polymer solution into an agitated bed of polymer particles. Typically, the introduction of polymer solution is accomplished by spraying the polymer solution into the bed; however, there are many variations of the process compatible with our invention.
Some polymers such as, for example, the polybutadienes, are so sticky that there is a strong tendency for polymer to build up on the rotor and walls of the purge column of a particle form evaporator. In addition, many polymers are so fluid that even with agitation the tendency towards formation of particles is so weak that the particle form evaporation process can be impracticable as a method for drying the polymer (i.e. removing solvent from the polymer). Successful removal of substantially all of the solvent from a polymer solution depends upon the ability to minimize the formation of agglomerates, i.e., the buildup of polymer on the purge column walls and rotor of a particle form evaporator, as well as the creation and maintenance of small polymer particles. Our invention makes practicable application of the particle form evaporation process to such polymers and facilitates the processing of polymers already suitable for the particle form evaporation process.